Green, Oolong Tea Significantly Reduce Risk of Hypertension
Yael Waknine
July 26, 2004 — Consumption of 120 mL per day or more of green or oolong tea in moderate strength for one year significantly reduces the risk of developing hypertension, according to results from an epidemiologic study published in the July 26 issue of the Archives of Internal Medicine.
"Tea contains more than 4000 chemical compounds that may affect the human body in many aspects," write Yi-Ching Yang, MD, MPH, and colleagues of the Medical College at National Cheng Kung University in Tainan, Taiwan, noting that studies exploring the preventative effects of polyphenolic flavonoids in tea against hypertension have yielded conflicting and inconsistent results thus far.
To examine the long-term effects of tea drinking on the risk of newly diagnosed hypertension, the investigators recruited 1,507 subjects aged 20 years and older with no history of the disease. Of these, 600 subjects (39.8%) were habitual tea drinkers, consuming 120 mL per day or more for at least one year.
Subjects who drank 120 mL to 599 mL of tea per day showed a 46% decrease in risk of developing hypertension compared with nonhabitual drinkers. The risk further decreased by 65% in those consuming 600 mL or more of tea each day.
Increasing the duration of tea consumption from one year to 10 years was not associated with further reduction of hypertension risk (odds ratio [OR] for 1-9 years, 0.54 vs. OR for 10+ years, 0.55).
Results were based on multiple logistic regression analysis and were adjusted using five covariates for lifestyle (total physical activity, high sodium intake, smoking, alcohol intake, and coffee intake), seven dietary factors (vegetable, fruit, unrefined grain, fish, milk, food with visible fat, and deep-fried food intake), and traditional risk factors for hypertension (age, sex, family history, body mass index, waist-hip circumference ratio, and socioeconomic index).
"To the best of our knowledge, this is the first study on the relationship between hypertension risk and tea consumption using detailed quantitative and qualitative information with multiple adjusted lifestyle and dietary factors," the authors write. "The possible protective effects of tea consumption on hypertension risk have been suggested by our epidemiological study.... However, more evidence from a long-term, randomized, prospective study is needed to fortify our preliminary inference about the link between tea consumption and hypertension risk."
This study was supported by grants from the National Science Council and the National Cheng Kung University Hospital in Taiwan.
Arch Intern Med. 2004;164:1534-1540
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